In their photosynthetic membranes, green plants and cyanobacteria contain a crucial enzyme, the oxygen-evolving complex, which catalyzes the oxidation of water to dioxygen. This proposal seeks to apply this technique of polarized XAS to probe the co-factors involved with Mn and the intermediate S states involved in oxygen evolution. Our goal in these near-edge studies is to progress from understanding the origins of Mn edge features in simple molecules to more complicated systems, including ultimately the four-Mn cluster of the OEC.